JPWO2012070441A1 - Laminated body and method for producing the same - Google Patents

Abstract

The laminate (10) is composed of a base material (1), an anchor layer (2) on one surface of the base material 1, and a fine cellulose fiber layer (3) containing fine cellulose fibers having a carboxyl group. The anchor layer (2) contains at least one resin having a carboxyl group, a sulfonic acid group, an amino group or a hydroxyl group, thereby forming a film with good adhesion and coating properties. There is an effect of suppressing deterioration with time of the fiber layer.

Description

  The present invention relates to a laminate formed of fine cellulose fibers that can be used as a coating agent, a functional laminate material, and the like, and a method for producing the laminate.

  In recent years, with increasing interest in environmental issues, natural polysaccharides such as starch, cellulose and chitin chitosan and their derivatives have attracted attention as biomass materials for conventional petroleum resins. In addition, a substrate made of a biodegradable resin that can be decomposed into water and carbon dioxide in the environment has attracted attention and is commercially available. Specifically, raw materials are aliphatic polyesters produced by microorganisms, naturally occurring starches, various polysaccharides such as cellulose and chitin chitosan and their derivatives, biodegradable resins and starches obtained by completely chemical synthesis. Examples include polylactic acid obtained by polymerizing the obtained lactic acid.

  Among these, cellulose produced in large quantities on the earth is fibrous and has high crystallinity, high strength and low linear expansion, and excellent chemical stability and safety to living bodies. Has been attracting attention. In particular, in recent years, fine cellulose fibers are expected to be used for various functional materials including packaging materials, and are actively developed.

  As a method for producing fine cellulose fibers, for example, in Patent Document 1, a TEMPO (2,2,6,6-tetramethylpiperidinooxy radical) catalyst is used to oxidize a part of hydroxyl groups to carboxyl groups. A method is described in which fine cellulose fibers are obtained by dispersing cellulose in a medium. According to this method, it is possible to relatively easily obtain fine cellulose fibers having a cellulose I-type crystal structure by utilizing the electrical repulsion action of a negatively charged carboxyl group.

  In Patent Document 2, oxidized cellulose obtained by TEMPO oxidation treatment is dispersed in water to prepare a gas barrier material containing fine cellulose fibers having an average fiber diameter of 200 nm or less. A method is described in which a gas barrier composite molded body is obtained by coating on a base material and drying.

JP 2008-1728 A JP 2009-57552 A

  However, the film formed by using the aqueous dispersion of fine cellulose fibers as described above has a rigid property and high elastic modulus of the fine cellulose fibers, a small area of contact with the substrate made of fiber shape, and In addition, there is a problem that adhesion to the substrate is low due to low reactivity. Further, many of these fine cellulose fibers have polar groups such as carboxyl groups introduced therein, and water-based solvents are used, so that there are problems with repelling, paintability, unevenness, and coatability. For example, when the adhesion is low, delamination occurs between the films when the film is used as a laminated material on a substrate. In addition, due to low repelling, paintability, unevenness, and coatability, a continuous and uniform film surface cannot be obtained, printability and processability are degraded, optical properties are degraded, and the coating film is barriered. When used as a material, there is a problem that good performance cannot be obtained. Furthermore, when a material such as paper or polylactic acid is used as a base material, it is a natural product, so compared to petroleum-derived synthetic resins such as PET, chemical instability and low molecular weight bleed, crystallization, Due to surface degradation, it is known that the wettability and adhesiveness during coating are lower, and the base material and coating film deteriorate over time after film formation, and the adhesiveness may be reduced. . Therefore, it is difficult to uniformly apply a coating liquid composed of an aqueous dispersion of fine cellulose fibers and to ensure adhesion with the base material. It was difficult to suppress degradation.

  The present invention has been made in view of the above problems, and uses a film base material, in particular, a naturally-derived material such as polylactic acid as a base material, and a coating liquid of fine cellulose fibers as a natural material as a coating material, and a gas barrier layer. Provides a laminated material that forms a film with good adhesion and coating properties when used as various functional material coatings such as a water vapor barrier layer, and that can suppress deterioration over time between the substrate and the fine cellulose fiber layer The purpose is to do.

  As means for solving the above-mentioned problems, the invention according to claim 1 is a fine cellulose comprising at least a base material, an anchor layer and a fine cellulose fiber having a carboxyl group on one surface of the base material. A laminate in which a fiber layer is provided in this order, wherein the anchor layer includes at least one resin having a carboxyl group, a sulfonic acid group, an amino group, or a hydroxyl group.

  In the invention according to claim 2, the fine cellulose fiber is an oxidized cellulose having a carboxyl group introduced by an oxidation reaction, and the content of the carboxyl group is 0.1 mmol / g or more and 5.5 mmol / g. It is the following, It is a laminated body of Claim 1.

  The invention according to claim 3 is the laminate according to claim 2, wherein the number average fiber diameter of the fine cellulose fibers is 0.001 μm or more and 0.200 μm or less.

  The invention according to claim 4 is the laminate according to claim 3, wherein the carboxyl group of the fine cellulose fiber forms an ammonium salt or an amine salt.

  The invention described in claim 5 is characterized in that the resin contained in the anchor layer is a polyester resin, a polyamide resin, a polyurethane resin, a polyacrylic acid resin, a polyolefin resin, or a copolymer thereof. Item 4. The laminate according to Item 3.

  The invention according to claim 6 is characterized in that the anchor layer includes at least a resin having a carboxyl group, and the carboxyl group of the resin forms an ammonium salt or an amine salt. It is a laminated body as described in above.

  The invention according to claim 7 is the laminate according to claim 5, wherein the anchor layer further contains a reactive compound having a carbodiimide group, an oxazoline group, an isocyanate group or an epoxy group. is there.

  The invention according to claim 8 is characterized in that the base material is made of a polyester resin, and the anchor layer includes a polyester resin having a carboxyl group and a reactive compound having a carbodiimide group or an oxazoline group. The laminate according to claim 7.

  The invention according to claim 9 is the laminate according to claim 8, wherein the polyester resin constituting the substrate is polylactic acid.

  The invention according to claim 10 is the laminate according to claim 7, wherein the molecular weight of the reactive compound is 1000 or more.

  The invention according to claim 11 is the laminate according to claim 7, wherein the acid value of the resin contained in the anchor layer is 12 or more.

  The invention according to claim 12 is the laminate according to claim 11, wherein the anchor layer has a thickness of 3 nm to 10 μm.

  The invention according to claim 13 is a laminate in which at least a base material and an anchor layer and a fine cellulose fiber layer containing fine cellulose fibers having a carboxyl group are provided in this order on one surface of the base material. And a carbodiimide group, an oxazoline group, an isocyanate group or an epoxy group on one surface of the substrate with at least one resin having a carboxyl group, a sulfonic acid group, an amino group or a hydroxyl group. A step of forming a coating film using a coating liquid containing a reactive compound having, a step of drying the coating film at 80 ° C. or less to form the anchor layer, and the fine cellulose fibers on the anchor layer And a step of forming a layer.

According to the present invention, when cellulose, which is a natural resource with a small environmental load, is effectively used and various functional material films such as a gas barrier layer and a water vapor barrier layer are formed, the coating properties and adhesion are excellent on the substrate. A laminated material that can be formed and includes the functional material coating can be provided.
In particular, a laminate material that can be formed on a substrate with good coatability and adhesion even when using a film substrate, a polylactic acid substrate, etc., and that suppresses the deterioration of the adhesion between the substrate and the fine cellulose fiber layer over time. Can provide. Thereby, a laminate having improved weather resistance, heat resistance and water resistance can be obtained.

It is sectional drawing which shows one Embodiment of the laminated body of this invention. It is sectional drawing which shows other one Embodiment of the laminated body of this invention.

Embodiments according to the present invention will be described below.
As shown in FIG. 1, the laminate (10) of the present invention comprises at least a base material (1), an anchor layer (2) on one surface of the base material (1), and a fine cellulose fiber having a carboxyl group. Are laminated in this order. The anchor layer (2) and the fine cellulose fiber layer (3) may be respectively laminated on both surfaces of the substrate (1).

  First, the fine cellulose fiber layer (3) will be described. The fine cellulose fiber layer includes at least fine cellulose fibers having a carboxyl group. The fine cellulose fiber which has a carboxyl group can be manufactured with the following method, for example.

(material)
A cellulose material is used as a raw material. The cellulose material may be subjected to pretreatment such as pulverization, explosion, swelling, purification, bleaching, dissolution regeneration, and alkali treatment. In particular, as a cellulose material, it is preferable to use naturally-derived cellulose having a crystal structure of cellulose I when obtaining a coating film having high gas barrier properties or a strong coating film. Examples of naturally occurring cellulose as a raw material include wood pulp, non-wood pulp, cotton pulp, bacterial cellulose, and squirt cellulose.

(Method of introducing carboxyl group)
As a method for introducing a carboxyl group into cellulose, a generally known chemical modification method can be used. As known in carboxymethylation, a method of introducing a carboxyl group by esterifying and etherifying a hydroxyl group of cellulose, a method of introducing a carboxyl group from a hydroxyl group by an oxidation reaction, and the like can be selected.
In particular, in order to obtain a coating film with high gas barrier properties and to introduce a carboxyl group without destroying the crystal structure, a nitroxy radical derivative is used as a catalyst, and hypohalite, halite, etc. A technique used as a cooxidant is preferred. In particular, an aqueous system containing sodium hypochlorite and sodium bromide using TEMPO (2,2,6,6-tetramethylpiperidinooxy radical) as a catalyst under alkaline conditions, preferably in the range of pH 9 to pH 11 The TEMPO oxidation method performed in a medium is preferable from the viewpoint of availability of reagents, cost, and reaction stability. In the above TEMPO oxidation method, alkali is consumed as the reaction proceeds, so it is preferable to add an aqueous alkaline solution as needed to keep the pH in the system constant.

  In TEMPO oxidation, the 6-position hydroxyl group of the pyranose ring (glucose) of the cellulose molecule is selectively oxidized, and a carboxyl group can be introduced via an aldehyde group. In addition, in TEMPO oxidation using natural cellulose, oxidation occurs only on the surface of crystalline microfibrils, which is a structural unit of cellulose, and no oxidation occurs inside the crystal. For this reason, fine cellulose fibers can be obtained while maintaining the crystal structure of cellulose I, and the fine cellulose fibers to be produced have characteristics such as high heat resistance, low linear expansion coefficient, high elastic modulus, and high strength.

As the reagents used for TEMPO oxidation, commercially available ones can be easily obtained. The reaction temperature is preferably 0 ° C. or more and 60 ° C. or less, and becomes a fine fiber in about 1 hour or more and 12 hours or less, and a sufficient amount of carboxyl groups can be introduced to show dispersibility.
TEMPOs and sodium bromide need only be used in a catalytic amount during the reaction, and can also be recovered after the reaction. In the above reaction system, sodium chloride is the only theoretical by-product, and the waste liquid can be easily treated with a low environmental burden.

  The amount of the carboxyl group can be adjusted by appropriately setting the TEMPO oxidation conditions. Cellulose fibers are dispersed in an aqueous medium by an electric repulsive force of a carboxyl group through a dispersion treatment step to be described later. Therefore, if the content of the carboxyl group is too small, the cellulose fiber cannot be stably dispersed in the aqueous medium. . On the other hand, if the amount is too large, the affinity for water increases and the water resistance decreases. In this respect, the carboxyl group content is preferably 0.1 mmol / g or more and 5.5 mmol / g or less, more preferably 0.1 mmol / g or more and 3.5 mmol / g or less, and even more preferably 0.6 mmol. / G to 2.5 mmol / g. In the process of introducing the carboxyl group, an aldehyde group that is an intermediate of the oxidation reaction is generated, and the aldehyde group remains in the final product. If the content of the aldehyde group is too large, the dispersibility in an aqueous medium is lowered or the color is changed after the film is formed. Therefore, the content of the aldehyde group is preferably 0.3 mmol / g or less. .

  The oxidation reaction is stopped by adding an excessive amount of other alcohol to completely consume the cooxidant in the system. As the alcohol to be added, it is desirable to use a low molecular weight alcohol such as methanol, ethanol or propanol in order to quickly terminate the reaction. Among these, ethanol is preferable in consideration of safety and by-products generated by oxidation.

(Recovery of oxidized cellulose)
After the oxidation reaction is stopped, the produced oxidized cellulose can be recovered from the reaction solution by filtration. In the oxidized cellulose after the termination of the reaction, the carboxyl group forms a salt using a metal ion derived from a co-oxidant or an inorganic alkali for pH adjustment as a counter ion. As a recovery method, a method in which the carboxyl group is filtered while forming a salt, a method in which an acid is added to the reaction solution and the pH is adjusted to 3 or less to filter it out as a carboxylic acid, and an organic solvent is added to cause aggregation. There is another way. Among them, a method of converting to carboxylic acid and recovering it from the viewpoint of handling property, yield, and waste liquid treatment is preferable. In addition, when preparing the fine cellulose fiber composition described later, since it is more miscible with the solvent if it does not contain a metal ion as a counter ion, a method of converting it to a carboxylic acid and recovering it is preferable.

  The metal ion content contained in the oxidized cellulose can be examined by various analysis methods. For example, it can be simply examined by elemental analysis using an EPMA method or an X-ray fluorescence analysis method using an electron beam microanalyzer. be able to. When recovered by the method of filtering while forming a salt, the metal ion content is 5 wt% or more, whereas when recovered by the method of filtering after carboxylic acid, the metal ion content is 1 wt. % Or less. In particular, when the oxidized cellulose is washed by the following method, the metal ion content is below the detection limit.

(Washing)
The recovered oxidized cellulose can be purified by repeated washing, and residues such as sodium chloride and ions that are catalysts and by-products can be removed. At this time, water is preferable as the cleaning liquid, and further, after adjusting and cleaning to acidic conditions of pH 3 or lower, more preferably pH 1.8 or lower using hydrochloric acid or the like, the metal ions are analyzed by the above analysis method. It can be made below the detection limit amount in. Alternatively, cleaning under acidic conditions may be performed a plurality of times in order to further reduce the amount of remaining metal ions. In addition, if salt or the like remains in the cellulose, it is difficult to disperse in the dispersion step described later.

  Next, the process of dispersing oxidized cellulose and preparing a fine cellulose fiber dispersion will be described.

(Dispersion process)
As a step of refining the washed oxidized cellulose, first, the oxidized cellulose is immersed in an aqueous medium that is a dispersion medium. At this time, the pH of the immersed liquid is, for example, 4 or less. Oxidized cellulose is insoluble in an aqueous medium and becomes a non-uniform suspension when immersed.

  In the oxidized cellulose suspension, the solid content concentration of oxidized cellulose is preferably 10% by mass or less, and more preferably 5% by mass or less. When the solid content concentration is 5% by mass or less, particularly 3% by mass or less, dispersibility and transparency are good. When solid content concentration exceeds 10 mass%, the viscosity of a dispersion liquid will raise remarkably and dispersion processing will become difficult. The minimum of solid content concentration is not specifically limited, What is necessary is just more than 0 mass%.

  Next, the pH of the oxidized cellulose suspension is adjusted to a range of pH 4 or more and pH 12 or less using an alkali. In particular, the pH is made alkaline between pH 7 and pH 12 to form a carboxylate. Thereby, since electrical repulsion between carboxyl groups is likely to occur, dispersibility is improved and fine cellulose fibers are easily obtained. Here, even if the pH is less than 4, the oxidized cellulose can be made into fine fibers by mechanical dispersion treatment, but the dispersion treatment requires a long time and high energy, and the fiber diameter of the obtained fiber is larger than that of the present invention. And the transparency of the dispersion is poor. On the other hand, when the pH exceeds 12, the reduction in molecular weight due to β-elimination reaction of oxidized cellulose and the yellowing of the dispersion are promoted during the dispersion treatment, resulting in poor film strength and transparency after film formation.

  As an alkali, it is not limited to a kind, Inorganic alkalis, such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, can be used. Alternatively, the pH can be adjusted using aqueous ammonia or organic alkali. Organic alkalis include various aliphatic amines, aromatic amines, amines such as diamines, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, benzyltrimethylammonium hydroxide, 2-hydroxyhydroxide. NR 4 OH such as ethyltrimethylammonium, etc. (wherein R is an alkyl group, benzyl group, phenyl group or hydroxyalkyl group, and four Rs may be the same or different) Organic onium compounds having hydroxide ions such as quaternary ammonium compounds, phosphonium hydroxide compounds such as tetraethylphosphonium hydroxide, oxonium hydroxide compounds, and sulfonium hydroxide compounds as counter ions. Even when an organic alkali is used, the fiber can be refined by a dispersion treatment similar to that when an inorganic alkali is used, regardless of the type of alkali.

  In particular, when an organic alkali is used as the alkali, the dispersion treatment can be performed in a shorter energy and in a shorter time than when an inorganic alkali having a metal ion as a counter ion is used, and the finally reached transparency of the dispersion liquid. Is also expensive. This is probably because the use of organic alkali has a larger counterion ion diameter, and thus has a greater effect of separating fine cellulose fibers in the dispersion medium.

  Furthermore, when an organic alkali is used, the affinity for an organic solvent is high, and therefore a fine cellulose fiber dispersion can be prepared even when an organic solvent such as alcohol is used as a dispersion medium. Furthermore, it is also possible to add an organic solvent to the fine cellulose fiber dispersion dispersed in an aqueous medium after the dispersion treatment. Examples of the aqueous medium include water or a mixed solvent of water and an organic solvent. Examples of the organic solvent include alcohols such as methanol, ethanol and 2-propanol (IPA), ketones such as acetone and methyl ethyl ketone (MEK), ethers such as 1,4-dioxane and tetrahydrofuran (THF), N, N -Dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetonitrile, ethyl acetate, glycerin and the like. Any one of these may be used alone, or two or more mixed solvents may be used.

  Furthermore, when an organic alkali is used, the viscosity and thixotropy of the fine cellulose fiber dispersion can be reduced compared to an inorganic alkali, in terms of ease of dispersion treatment and ease of application in the coating process described below. It is advantageous. Usually, the fine cellulose fiber dispersion becomes a gel, and the viscosity increases as the concentration is increased. Therefore, a large amount of energy is required in the dispersion treatment, and the dispersion treatment becomes difficult. Since the viscosity of the fiber dispersion is lowered, the dispersion treatment is facilitated. By the combination of the organic alkali and the solvent, the viscosity characteristics of the dispersion liquid can be adjusted, and the coating property can be improved.

In addition, as described later, when the anchor layer (2) contains a compound capable of reacting with a carboxyl group such as a carbodiimide group, an oxazoline group, an epoxy group or an amino group, ammonia having a low boiling point is used. When an organic alkali such as triethylamine is used as the alkali of the fine cellulose fiber dispersion, the alkali volatilizes during the drying after coating or the subsequent aging / curing treatment, the carboxyl group increases in reactivity, and the anchor layer (2 The reaction with the reactive compound contained in) proceeds further, and the effect of further improving adhesion and preventing deterioration with time is high. For the above reason as well, the carboxyl group of the fine cellulose fiber contained in the fine cellulose fiber layer forms an ammonium salt or amine salt that is more likely to react than the inorganic salt formed by the inorganic alkali. Preferably it is. Here, examples of the amine salt include triethylamine salt and tetramethylamine salt.
Further, the carboxyl group of the fine cellulose fiber does not form a salt, and even if it exists in the carboxyl group state, that is, in the state of “—COOH”, the reaction is likely to proceed, which is preferable.

  As the method for dispersing the oxidized cellulose suspension, various known dispersion treatments can be used. For example, homomixer processing, mixer processing with rotary blade, high pressure homogenizer processing, ultra high pressure homogenizer processing, ultrasonic homogenizer processing, nanogenizer processing, disc type refiner processing, conical type refiner processing, double disc type refiner processing, grinder processing, ball mill processing , Kneading treatment by a biaxial kneader, underwater facing treatment, and the like. Among these, the mixer treatment with a rotary blade, the high-pressure homogenizer treatment, the ultra-high pressure homogenizer treatment, and the ultrasonic homogenizer treatment are preferable from the viewpoint of miniaturization efficiency. In addition, it is also possible to perform dispersion by combining two or more processing methods among these processes.

When the dispersion treatment is performed, the oxidized cellulose suspension becomes a transparent dispersion that is visually uniform. Oxidized cellulose is refined by the dispersion treatment to form fine cellulose fibers.
The fine cellulose fiber after the dispersion treatment has a number average fiber diameter (width in the minor axis direction of the fiber) of preferably 0.001 μm or more and 0.200 μm or less, more preferably 0.001 μm or more and 0.050 μm or less. . The number average fiber diameter of the fine cellulose fibers can be confirmed by a scanning electron microscope (SEM) or an atomic force microscope (AFM). If the dispersion is insufficient or non-uniform and some of the fibers have a large fiber diameter, the transparency and smoothness of the film will be significantly reduced when a coating solution containing fine cellulose fibers is formed. There's a problem.

  As a coating liquid containing a fine cellulose fiber having a carboxyl group produced by the above method or the like, the fine cellulose fiber dispersion can be used as it is, or a known resin or solvent may be added. . Moreover, the fine cellulose fiber which has the carboxyl group manufactured by said method etc. is isolated, well-known resin and a solvent may be mixed and a coating liquid may be prepared separately.

  A fine cellulose fiber layer is formed by apply | coating the coating liquid containing the fine cellulose fiber which has a carboxyl group. It does not specifically limit as a method of apply | coating the coating liquid containing a fine cellulose fiber, Well-known methods, such as a coating method and a casting method, can be utilized. Coating methods include gravure coating, gravure reverse coating, roll coating, reverse roll coating, micro gravure coating, comma coating, air knife coating, bar coating, Mayer bar coating, dip coating, and die coating. Method, spray coating method and the like, and any method may be used.

  The thickness of the fine cellulose fiber layer is preferably 0.05 μm or more and 20 μm or less, and more preferably 0.1 μm or more and 2 μm or less. If the thickness of the fine cellulose fiber layer is larger than 20 μm, the processability may be inferior, and if the thickness of the fine cellulose fiber layer is smaller than 0.05 μm, the gas barrier property may be lowered.

  The fine cellulose fiber layer may contain various additives such as inorganic layered compounds and organometallic compounds in addition to the fine cellulose fibers having a carboxyl group.

  Inorganic layered compounds include kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, beidellite, hectorite, saponite, stevensite, tetrasilic mica, sodium teniolite, muscovite, marga Light, talc, vermiculite, phlogopite, xanthophyllite, chlorite and the like can be used. These inorganic layered minerals may be natural or synthetic. In particular, the inorganic layered compound is preferably montmorillonite in terms of gas barrier properties, dispersibility, ease of mixing with fine cellulose fibers, and cohesive strength of the film. The blending amount of these inorganic layered minerals is not particularly limited, and can be added within a range satisfying the required specifications within a range of 0.01% to 99%. In particular, from the viewpoint of adhesion of the laminate, it is more preferably in the range of 0.01% to 67%.

Moreover, as an organometallic compound, the following general formula,
A _m M (OR) _nm
(In the formula, A is composed of one or more types of carbon main chain having 1 to 10 carbon atoms, M is a metal element, R is an alkyl group, n is an oxidation number of the metal element, and m is a substitution number ( 0 ≦ m <n)), or a hydrolyzate or polymer of the organometallic compound. Specific examples include metal alkoxides of Ti, Zr, and Si, and particularly silicon alkoxide exhibits good performance. Tetraalkoxy compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane or polymers thereof, trialkoxy compounds such as trimethoxysilane, triethoxysilane, tripropoxysilane or polymers thereof, dimethoxysilane, diethoxysilane, etc. Dialkoxy or a polymer thereof, other than that, methyltrimethoxysilane having a C-Si bond, methyltriethoxysilane, methyldimethoxysilane, etc., or having a functional group, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropylto Examples include reethoxysilane and N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane.

  Next, the base material (1) will be described. It does not specifically limit as a base material, It can select and use suitably according to a use from the various sheet-like base materials (a film-form thing is included) generally used. Examples of such base materials include paper, paperboard, biodegradable plastics such as polylactic acid and polybutyl succinate, polyolefin resins (polyethylene, polypropylene, etc.), polyester resins (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate). Phthalates, polylactic acid, etc.), polyamide resins (nylon-6, nylon-66, etc.), polyvinyl chloride resins, polyimide resins, copolymers of any two or more of these monomers. . The base material may contain known additives such as an antistatic agent, an ultraviolet absorber, a plasticizer, a lubricant, and a colorant.

  In particular, using base materials made of biomass-derived materials such as paper, polylactic acid, biodegradable plastics such as polybutyl succinate, bio-polyethylene, etc. It is preferable because it can maximize the use.

  The base material may be subjected to surface treatment such as corona treatment, plasma treatment, ozone treatment, flame treatment and the like on the surface. By performing the surface treatment, wettability and adhesion with a layer laminated on the surface (for example, a fine cellulose fiber layer) are further improved. These surface treatments can be performed by known methods.

  The thickness of the substrate can be appropriately set according to the use of the laminated material. For example, when used as a packaging material, it is usually in the range of 5 μm to 200 μm, preferably 10 μm to 100 μm. From the viewpoint of cost and resource saving, 10 μm or more and 30 μm or less is most preferable.

  In particular, the laminate of the present invention has a carboxyl group, a sulfonic acid group, an amino group or a hydroxyl group in the base material, the anchor layer, and the fine cellulose fiber layer, and their polarities attract each other, or the anchor layer Since the adhesion, paintability, and stability over time are improved by the reaction with the reactive compound described later contained in the base material, the base material preferably has a carboxyl group, a sulfonic acid group, an amino group, or a hydroxyl group. In particular, a polyester resin is preferable.

  In addition, ordinary polyester resins have only a few terminal carboxyl groups left, but these polyester resins are modified and modified to introduce more carboxyl groups and sulfonic acid groups to the surface or inside. The polyester resin is more preferred because it has a high effect of improving adhesion, paintability and stability over time. Further, among polyester resins, it is more preferable to use a base material made of polylactic acid because of the advantage of making the best use of the advantages of the fine cellulose fibers which are the above-mentioned natural product-derived materials with less environmental load.

  Next, the anchor layer (2) will be described. The laminate of the present invention is characterized by having an anchor layer. As a result, the fine cellulose fibers contained in the fine cellulose fiber layer have a rigid property and a high elastic modulus, and because of the fiber shape, the area of the contact point with the substrate is small, and the reactivity is low. The problem is that the adhesion to the substrate is low, the problem that the dispersion medium used in the fine cellulose fiber is water-based, the problem with respect to the repelling, paintability and coating property, and the chemical anxiety of the substrate A water-based dispersion of fine cellulose fibers that solves the problem of deterioration of adhesion and substrate deterioration due to qualitative and low molecular weight molecular bleeding, crystallization, and surface deterioration. It is possible to uniformly coat the coating liquid consisting of the above and to secure the adhesion to the substrate, and to suppress the adhesion with time and the deterioration of the substrate and fine cellulose fibers.

  The anchor layer preferably contains at least one resin having a carboxyl group, a sulfonic acid group, an amino group or a hydroxyl group. When the resin is included, the polarities of the carboxyl group, sulfonic acid group, amino group or hydroxyl group present in the base material or fine cellulose fiber attract each other, and by reacting with the reactive compound contained in the anchor layer, the adhesion In addition, paintability and stability over time are improved. In particular, by including a resin having a carboxyl group, the effect of improving these performances is remarkable due to the interaction between polarities, the covalent bond due to the reaction with the reactive compound contained in the anchor layer, and the synergistic effect thereof. . The resin contained in the anchor layer may have only one type of functional group or a plurality of functional groups. Moreover, you may have functional groups other than the said functional group, if the above-mentioned effect is not inhibited.

  As the resin having these functional groups, a polyester resin, a polyamide resin, a polyimide resin, a polyurethane resin, a polyacrylic acid resin, a polyolefin resin, or a copolymer thereof can be used. These resins may be acid-modified resins, resins modified by oxidation treatment, or resins having the above functional groups or other functional groups introduced by chemical modification. Among these resins, in particular, polyurethane resins, polyacrylic acid resins, and polyester resins are highly effective in improving adhesion and coating properties with fine cellulose fibers. In addition, when the base material is a polyester resin, if a polyester resin is also used for the anchor layer, the interaction between polarities, the intermolecular force, the covalent bond due to the reaction with the reactive compound contained in the anchor layer, and those Due to the synergistic effect, the effect of improving the adhesion between the layers and the effect of stability over time are particularly remarkable. For example, when a polylactic acid base material is used and a polylactic acid resin is used as an anchor layer, the adhesion with the fine cellulose fiber layer is improved especially on a polylactic acid base material that has poor adhesion to most coatings. be able to. The said resin should just be contained at least 1 type in the anchor layer, and may be contained combining multiple said resin. Moreover, as long as the above-mentioned effect is not inhibited, you may contain in combination with resin other than the said resin.

  Moreover, 12 or more are preferable and, as for the acid value of resin contained in an anchor layer, 20 or more are more preferable. The acid value affects the amount of the functional group and the above-described effects. If the acid value is less than 12, the effect of improving adhesion, paintability, and stability over time is small. If it is 20 or more, these effects are high, and the reactivity with the compound contained in the anchor layer is also good. If it is 50 or more, the interaction between polarities is large even if there is no reactive compound or there is little. appear. However, if it is larger than 200, it may affect the water resistance and blocking properties, so 12 or more and 200 or less are more preferable.

In addition, when the resin contained in the anchor layer has a carboxyl group, the carboxyl group forms various salts using metal hydroxides such as sodium hydroxide and potassium hydroxide, organic ammonium such as ammonium and diethylammonium. can do. The state of these carboxyl groups greatly affects the solubility of the resin and the type of solvent. In particular, when a reactive compound described later is included, it is preferable that the carboxyl group of the resin included in the anchor layer forms an ammonium salt or an amine salt because the reaction proceeds at a low temperature. Here, examples of the amine salt include triethylamine salt and tetramethylamine salt.
Further, the carboxyl group of the resin contained in the anchor layer is preferable because the reaction proceeds at a low temperature even when it does not form a salt and exists in the carboxyl group state, that is, in the state of “—COOH”.

  The thickness of the anchor layer is preferably 3 nm or more and 10 μm or less. When the thickness is less than 3 nm, the width of the fine cellulose fiber is smaller than that of the fine cellulose fiber, and the number of contacts is reduced. On the other hand, if it exceeds 10 μm, the film is too thick and the efficiency is poor, and warping and curling occur due to distortion of the anchor layer and the fine cellulose fiber layer. From the aspect of warping and curling, 3 nm or more and 5 μm or less are preferable. In particular, 3 nm or more and 2 μm or less are more preferable in terms of cost and drying efficiency.

Furthermore, the anchor layer preferably contains a reactive compound. These reactive compounds promote the reaction with the resin contained in the anchor layer, and may react with a functional group such as a carboxyl group or a hydroxyl group of the fine cellulose fiber, and further with a functional group contained in the substrate. preferable. Due to these synergistic effects, adhesion between layers, coating property, and stability over time can be exhibited. Although it does not specifically limit as a reactive compound, The compound which has a carbodiimide group, an oxazoline group, an isocyanate group, an epoxy group, an amino group etc. is used preferably. Above all, compounds containing carbodiimide groups, oxazoline groups, and isocyanate groups can react efficiently with hydroxyl groups and carboxyl groups contained in the base material, anchor layer, and fine cellulose fiber layer, and can react at low temperatures. Therefore, high reactivity is exhibited when using a base material which is large in expansion and contraction due to heat, such as polyester and polyolefin, particularly polylactic acid.
Moreover, since the carbodiimide group and the oxazoline group react slowly at a low temperature such as room temperature, the adhesion between the base material such as polylactic acid, the anchor layer, and the fine cellulose fiber can be stabilized over time. In particular, when the anchor layer is formed, the drying temperature is kept at a low temperature of 80 ° C. or lower, and a fine cellulose fiber layer is provided on the anchor layer so that unreacted carbodiimide groups and oxazoline groups in the anchor layer It is possible to prevent deterioration of the cellulose fiber layer and decrease in adhesion. The drying temperature when forming the anchor layer has a great effect of preventing deterioration and deterioration of adhesion, and especially when using polylactic acid with low heat resistance as the base material, the deformation of the base material is minimized. In terms of suppression, it is more preferable to set the temperature to 60 ° C. or lower.

Moreover, it is preferable that the molecular weight of these reactive compounds is 1000 or more. When the molecular weight of the reactive compound is less than 1000, the anchor layer becomes brittle, and the adhesion with a layer made of rigid fine cellulosic fibers or a hard substrate is not stable and tends to be weak. For example, when a reactive compound having a molecular weight greater than 1000 is used, the strength of the weakest layer as viewed in the thickness direction of the laminate can be kept at 1.5 N or more when measured as the laminate strength.
Further, the upper limit of the molecular weight of the reactive compound is not particularly specified, but can be appropriately adjusted in consideration of the coating solution viscosity, film strength, and thermal characteristics of the anchor layer.

  In addition to the anchor layer (2) and the fine cellulose fiber layer (3), the laminate (10) of the present invention has various functional layers such as an inorganic vapor deposition layer and a heat-sealable thermoplastic resin layer as necessary. May be.

  An inorganic vapor deposition layer is a layer provided in order to further improve the gas barrier property of a laminated body, and water vapor | steam barrier property, for example, consists of aluminum oxide, magnesium oxide, silicon oxide, etc. Examples of the method for forming the inorganic vapor deposition layer include a vacuum vapor deposition method, a sputtering method, and a plasma vapor deposition method. The inorganic vapor deposition layer is preferably provided on the surface of the fine cellulose fiber layer.

  Further, the heat-sealable thermoplastic resin layer is provided as a sealing layer when a bag-like package or the like is formed using the laminate of the present invention. FIG. 2 shows a laminate (20) provided with the thermoplastic resin layer of the present invention. The thermoplastic resin layer (5) is laminated via the adhesive layer (4) on the fine cellulose fiber layer (3) laminated via the anchor layer (2) on one surface of the substrate (1). The

Examples of the thermoplastic resin layer (5) include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene. A heat-weldable film made of a resin such as an acrylic ester copolymer or a metal cross-linked product thereof is used.
As a method for forming the thermoplastic resin layer on the fine cellulose fiber layer, a film that is a thermoplastic resin layer is bonded to the surface of the fine cellulose fiber layer using an adhesive such as a two-component curable urethane resin. A laminating method or the like is generally used, but any of coating, non-solvent laminating, wet laminating, extrusion laminating and the like can be laminated by a known method.
Thus, the thermoplastic resin layer is preferably provided on the surface of the fine cellulose fiber layer via the adhesive layer. In addition to the adhesive layer, other layers such as a printing layer may be provided between the fine cellulose fiber layer and the thermoplastic resin layer.

  Examples and comparative examples will be described below. In addition, this invention is not limited by these Examples.

(Preparation method 1 of oxidized cellulose)
Softwood bleached pulp, which is widely available as cellulose, was used.
60 g of cellulose (in terms of absolute dry mass) was added to 1000 g of distilled water, stirred and swollen, and then defibrated with a mixer. To this, 2200 g of distilled water and 0.6 g of TEMPO previously dissolved in 400 g of distilled water and 6 g of sodium bromide were added, and 172 g of a 2 mol / L sodium hypochlorite aqueous solution was added dropwise to oxidize. The reaction was started. The reaction temperature was always kept below 20 ° C. During the reaction, the pH in the system was lowered, but a 0.5 N NaOH aqueous solution was sequentially added to adjust the pH to 10. And when it was made to react for 4 hours, ethanol 60g was added and reaction was stopped. Subsequently, 0.5N HCl was added dropwise to the reaction solution to lower the pH to 2. This reaction solution was filtered using a nylon mesh, the solid content was further washed several times with water, the reaction reagent and by-products were removed, and the oxidized cellulose 1 containing water with a solid content concentration of 7% was obtained.

(Preparation method 2 of oxidized cellulose)
Oxidized cellulose 2 was obtained by the same preparation method as Preparation Method 1 except that the reaction temperature was 30 ° C.

(Measurement of the amount of functional groups introduced)
0.2 g of freeze-dried oxidized cellulose in terms of absolute dry mass was weighed into a beaker, and distilled water was added to make 60 g. 0.5 mL of 0.1 M NaCl aqueous solution was added, the pH was adjusted to 2 with 0.5 M hydrochloric acid, and 0.5 M NaOH aqueous solution was dropped to conduct conductivity measurement. The measurement was continued until the pH reached about 11. Since the portion corresponding to the neutralization stage of the weak acid is the amount of carboxyl groups, when the amount of NaOH added is read from the obtained conductivity curve, the content of carboxyl groups in oxidized celluloses 1 and 2 is 1.6 mmol / g, 2.5 mmol / g.

  Next, 20 g of 0.5 M acetic acid, 60 mL of distilled water and 1.8 g of sodium chlorite were added to 2 g of wet oxidized cellulose in terms of absolute dry mass, adjusted to pH 4 and reacted for 48 hours. Thereafter, when the carboxyl group content was measured by the same method as described above, it was 1.8 mmol / g and 2.6 mmol / g, respectively. From this, the aldehyde group content could be calculated as 0.2 mmol / g and 0.1 mmol / g, respectively. Table 1 shows the carboxyl group content and aldehyde group content of oxidized celluloses 1 and 2.

(Preparation of fine cellulose fiber dispersion 1)
Distilled water and 0.1N ammonia aqueous solution were added to 57.14 g (solid content 4 g) of the oxidized cellulose 1 having a solid content concentration of 7% prepared as described above to obtain 400 g of oxidized cellulose suspension having a pH of 10. The prepared suspension was processed for 60 minutes with a mixer equipped with a rotary blade to obtain a fine cellulose fiber dispersion 1.

(Preparation of fine cellulose fiber dispersion 2)
Distilled water and 0.5N sodium hydroxide aqueous solution were added to 57.14 g (solid content 4 g) of the oxidized cellulose 1 having a solid content concentration of 7% prepared as described above to obtain 400 g of oxidized cellulose suspension having a pH of 6.8. The prepared suspension was treated with a high-pressure homogenizer to obtain a fine cellulose dispersion 2.

(Preparation of fine cellulose dispersion 3)
To 57.14 g (solid content 4 g) of oxidized cellulose 2 having a solid content concentration of 7% prepared above, 2 g of distilled water and inorganic layered mineral (montmorillonite) were added in solid content, and 0.5N sodium hydroxide aqueous solution was added. 400 g of oxidized cellulose suspension was used. The prepared suspension was treated with a mixer with a rotary blade for 20 minutes to obtain a fine cellulose fiber dispersion 3.

  Table 2 shows the oxidized cellulose, alkali and additives used in the preparation of the fine cellulose dispersions 1 to 3. Further, the number average fiber diameter of the fine cellulose fibers contained in the fine cellulose dispersions 1 to 3 was obtained from an average of 20 points of the height observed with an atomic force microscope (AFM). The results are also shown in Table 2.

(Coating solution for anchor layer formation)
By combining the following resins 1 to 7 and the following additives 1 to 3, 10 parts by weight of the additive is mixed with 100 parts by weight of the resin to form an anchor layer (coating liquid for forming an anchor layer) 1 to 1 10 was prepared. Table 3 shows the combinations of resins 1 to 7 and additives 1 to 3 in the anchor layer forming coating solution, the solvent used, and the solid content concentration.

[Resin 1-7]
Resin 1 ... Polyester WR-961
(Carboxyl group-containing polyester, ammonium salt type, acid value 60-70)
Nippon Synthetic Chemical Co., Ltd. Resin 2 Polyester WR-901
(Sodium sulfate group-containing polyester, acid value of 5 or less)
Nippon Synthetic Chemical Co., Ltd. Resin 3 ... Arrow Base SB-1010
(Carboxyl group-containing acid-modified polyolefin, ammonium salt type,
Acid value 12 or more)
Unitika Resin 4 NT-Hilamic
(Polyurethane)
Made by Dainichi Seika Co., Ltd. Resin 5: Bye Ecole BE-600
(Polylactic acid)
Toyobo resin 6 ... chitosan
Dainichi Seisaku Co., Ltd. Resin 7… Dianar BR-107
(acrylic)
Made by Mitsubishi Rayon

[Additives 1-3]
Additive 1 ... SV-02
(Water-soluble polycarbodiimide, molecular weight 1000 or more)
Nisshinbo additive 2 ... Epocross WS-500
(Oxazoline molecular weight 70000)
Nippon Shokubai additive 3 ... Takenate A65
(Isocyanate)
Mitsui Chemicals additive 4 ... EX614
(Epoxy)
Made by Nagase ChemteX

<Examples 1-9>
A 25 μm thick polylactic acid film having a corona-treated surface was prepared as a substrate. On the corona-treated surface of the base material, anchor layer forming coating solutions 1 to 9 were applied using a bar coater, and then dried at 60 ° C. for 20 minutes to form an anchor layer having a thickness of about 0.2 μm. .
On the anchor layer, the fine cellulose fiber dispersion 1 was applied using a bar coater and then dried at 60 ° C. for 20 minutes to form a fine cellulose fiber layer having a thickness of about 0.2 μm.
Further, a polypropylene film having a thickness of 70 μm, which is a thermoplastic resin layer that can be heat-welded, is bonded to the fine cellulose fiber layer by dry lamination using a urethane polyol-based adhesive, and a base material / anchor layer / fine cellulose. A laminate of fiber layer / adhesive layer / thermoplastic resin layer was obtained.

<Examples 10 to 12>
As a substrate, a polyethylene terephthalate film having a thickness of 25 μm and a corona-treated surface was prepared. On the corona-treated surface of the base material, the anchor layer forming coating solutions 2, 3, and 4 are applied using a bar coater, and then dried at 80 ° C. for 20 minutes to form an anchor layer having a thickness of about 0.2 μm. Formed.
On the anchor layer, the fine cellulose fiber dispersion 2 was applied using a bar coater and then dried at 100 ° C. for 20 minutes to form a fine cellulose fiber layer having a thickness of about 0.2 μm.
Further, a polypropylene film having a thickness of 70 μm, which is a thermoplastic resin layer, is bonded to the fine cellulose fiber layer by dry lamination using a urethane polyol-based adhesive, and the base material / anchor layer / fine cellulose fiber layer / adhesion. A layer / thermoplastic resin layer laminate was obtained.

<Example 13>
A stretched polypropylene film having a thickness of 20 μm whose surface was corona-treated was prepared as a substrate. On the corona-treated surface of the substrate, the anchor layer-forming coating solution 4 was applied using a bar coater, and then dried at 80 ° C. for 20 minutes to form an anchor layer having a thickness of about 1 μm.
On the anchor layer, the fine cellulose fiber dispersion 3 was applied using a bar coater, and then dried at 80 ° C. for 20 minutes to form a fine cellulose fiber layer having a thickness of about 0.5 μm.
Further, a polypropylene film having a thickness of 70 μm, which is a thermoplastic resin layer, is bonded to the fine cellulose fiber layer by dry lamination using a urethane polyol-based adhesive, and the base material / anchor layer / fine cellulose fiber layer / adhesion. A layer / thermoplastic resin layer laminate was obtained.

<Comparative Example 1>
A laminate was obtained in the same manner as in Examples 1 to 9 except that the anchor layer was not formed on the corona-treated surface of the substrate and the fine cellulose fiber dispersion 1 was directly applied using a bar coater.

<Comparative example 2>
A laminate was obtained in the same manner as in Examples 10 to 12 except that the anchor layer forming coating solution 9 was used as the anchor layer forming coating solution. In addition, since the coating liquid 10 for anchor layer formation was poor in coating properties and it was difficult to apply the fine cellulose fiber dispersion directly to the formed anchor layer, an excessive amount of corona treatment was added to the anchor layer surface, and then the fine coating was performed. A cellulose fiber layer was provided.

[Coating property evaluation]
In the process of applying the fine cellulose fiber dispersion when preparing the laminates of Examples 1 to 13 and Comparative Examples 1 and 2, in Examples 1 to 13, the wettability of the fine cellulose fiber dispersion is good. In particular, no repelling or unevenness was observed. In Comparative Example 2, since the corona treatment was excessively applied to the anchor layer surface, the wettability of the fine cellulose fiber dispersion was good to some extent.
On the other hand, in Comparative Example 1, the wettability was poor, and the repelling and unevenness of the fine cellulose fiber dispersion could be visually observed.

[Measurement of oxygen permeability under normal conditions]
The oxygen permeability (cm ³ / m ² / day / atm) of the laminate was measured using an oxygen permeability measuring apparatus MOCON OX-TRAN 2/21 (manufactured by Modern Control Co., Ltd.) at 25 ° C. and 40% RH atmosphere. By measuring, the oxygen barrier property under normal conditions was evaluated.

[Measurement of water vapor transmission rate under high humidity conditions]
The water vapor permeability (g / m ² / day) of the laminate is measured by the cup method in accordance with JIS Z0208 in an atmosphere of 40 ° C. and 90% RH, thereby evaluating water vapor barrier properties under high humidity conditions. did.

[Adhesion test]
The laminate was cut into strips having a width of 15 mm and a length of 100 mm, and a peeling rate of 300 mm / min. T-type peel strength was measured.

[Stability test over time]
The laminate was stored for 1 week in an environment of 40 ° C. and 90%, and the adhesion was evaluated in the same manner as in the adhesion test method described above.

  The above evaluation results are shown in Table 4.

From the above results, the laminate of the present invention has good coatability and coatability, and can form a uniform film without unevenness of the fine cellulose fiber layer. It can be said that the permeability and water vapor permeability were small, and good barrier properties were exhibited.
Moreover, the thing of the Example also showed the favorable result regarding the adhesiveness, and also showed the favorable result regarding the temporal stability. In addition, these effects were larger as the anchor layer contained a reactive compound, and those processed at a drying temperature of 60 ° C. or less after application of the anchor layer forming coating solution.

  The laminate of the present invention is used in the field of packaging materials such as foods and pharmaceuticals, in order to protect the contents, such as films and sheets that block gas such as oxygen and water vapor that permeate the packaging material, bottles, etc. It can be used for molded products.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Anchor layer 3 ... Fine cellulose fiber layer 4 ... Adhesive layer 5 ... Thermoplastic resin layer 10, 20 ... Laminate

Claims (13)

At least a base material, and a laminated body in which an anchor layer and a fine cellulose fiber layer containing fine cellulose fibers having a carboxyl group are provided in this order on one surface of the base material,
The laminated body, wherein the anchor layer contains at least one resin having a carboxyl group, a sulfonic acid group, an amino group, or a hydroxyl group.   2. The fine cellulose fiber is oxidized cellulose into which carboxyl groups are introduced by an oxidation reaction, and the content of the carboxyl groups is 0.1 mmol / g or more and 5.5 mmol / g or less. The laminated body as described in.   The number average fiber diameter of the said fine cellulose fiber is 0.001 micrometer or more and 0.200 micrometer or less, The laminated body of Claim 2 characterized by the above-mentioned.   The laminate according to claim 3, wherein the carboxyl group of the fine cellulose fiber forms an ammonium salt or an amine salt.   4. The laminate according to claim 3, wherein the resin contained in the anchor layer is a polyester resin, a polyamide resin, a polyurethane resin, a polyacrylic acid resin, a polyolefin resin, or a copolymer thereof.   The laminate according to claim 3, wherein the anchor layer includes at least a resin having a carboxyl group, and the carboxyl group of the resin forms an ammonium salt or an amine salt.   The laminate according to claim 5, wherein the anchor layer further contains a reactive compound having a carbodiimide group, an oxazoline group, an isocyanate group or an epoxy group.   The laminate according to claim 7, wherein the base material is made of a polyester resin, and the anchor layer includes a polyester resin having a carboxyl group and a reactive compound having a carbodiimide group or an oxazoline group.   The laminate according to claim 8, wherein the polyester resin constituting the base material is polylactic acid.   The laminated body according to claim 7, wherein the molecular weight of the reactive compound is 1000 or more.   The laminate according to claim 7, wherein an acid value of the resin contained in the anchor layer is 12 or more.   The laminate according to claim 11, wherein the anchor layer has a thickness of 3 nm to 10 μm. At least a base material, and a manufacturing method of a laminate in which an anchor layer and a fine cellulose fiber layer containing fine cellulose fibers having a carboxyl group are provided in this order on one surface of the base material,
On one surface of the substrate, a coating containing at least one kind of resin having a carboxyl group, a sulfonic acid group, an amino group or a hydroxyl group and a reactive compound having a carbodiimide group, an oxazoline group, an isocyanate group or an epoxy group. Forming a coating film using the liquid;
Drying the coating film at 80 ° C. or less to form the anchor layer;
And a step of forming the fine cellulose fiber layer on the anchor layer.

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